This invention relates generally to service life of vehicles and, more specifically, to discovering and recovering unused portions of service life of vehicles.
Owners of aircraft, such as the military, face a dilemma of trading off between the cost of new replacement aircraft and the cost of modernization and upgrades to existing aircraft. Modernization and upgrades are generally less expensive than new aircraft, but can be financially justified when sufficient service life remains in an aircraft. Traditional methods employed for determining service life expended and service life remaining are based solely upon cumulative flight hours and maximum load assumptions. For aircraft flown under less demanding conditions, actual aircraft service life can be significantly greater than the determined service life.
When modernizations and upgrades are considered for older aircraft, fatigue testing is used to determine service life remaining. Fatigue testing is destructive, very expensive, and time consuming.
Attempts have been made to determine service life of critical aircraft components. One attempt uses a plurality of stress gauges mounted to various locations of the critical aircraft components. The stress gauges are electrically linked to a data processing computer that computes service life based on measured stresses at the gauges. Attaching and wiring a new or an old aircraft with the number of gauges necessary for retrieving adequate stress information is prohibitively expensive and can not possibly identify all the incurred stresses.
Therefore, there exists an unmet need to non-destructively determine service life in a less costly way.
The present invention reduces time and cost required to develop a business case for proposed modernizations and upgrades of older aircraft, recovers unused service life in legacy aircraft structures, and provides continuous, even real-time, assessment of service life expended and remaining.
The present invention provides a system on-board a vehicle for determining cycles to failure of the vehicle. An embodiment of the system includes a vehicle attitude reference or navigation system, a memory, and a processing component. The vehicle navigation system generates distance values in at least one of 6 degrees of freedom. The distance values result from detected accelerations in at least one of the 6 degrees of freedom. The memory stores ductility and spring constant values for at least one of the 6 degrees of freedom for one or more vehicle parts. The processing component converts the distance values to strain values, and determines cycles-to-failure for one or more of the vehicle parts based on the strain values and associated ductility and spring constant values. The processing component also subtracts the determined cycles to failure for each of the parts from previously-predicted cycles-to-failure, and stores the result of the subtraction in the memory.
According to an aspect of the invention, an embodiment of the system also suitably includes a vehicle crew user interface that alerts the vehicle crew when an alert signal is received from the processing component if the determined cycles-to-failure is less than the previously-predicted cycles-to-failure.